1st gen 12A vs. 1st gen 13B
i know this might be a stupid question but im going to ask anyways. which engine can you squeeze more power out of the 12A or 13B? now im not talkin about any kinda porting at all nor any kinda forced induction im talkin straight up HP. bolt ons like headers, exhust, after market carb sh*t like something that a normal joe can afford, and also about without going with an aftermarket ecu.i know that Hp is only dollar bills way in many cases many many dollar bills away. i did do a lil sheaching but i could have missed something or just not searched enough if this has been disscussed b4 can you pls point me in the right direction. thanks guys
charles |
depending on which 13-B. 4-port or 6-port
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Originally Posted by wackyracer
depending on which 13-B. 4-port or 6-port
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With no porting: 13b. With porting: 12 A or 13b 4 port (6 port is just crap for porting)
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It doesn't depend on if it's a 6 or 4 port. The 13b is a larger engine, it moves more air, therefore it will make more power given equal modifications, compensating for the increased air and fuel needs of the larger engine, of course.
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But you can't properly port the (is it exhaust or intake) ports on a 6 port.
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Originally Posted by purple82
It doesn't depend on if it's a 6 or 4 port. The 13b is a larger engine, it moves more air, therefore it will make more power given equal modifications, compensating for the increased air and fuel needs of the larger engine, of course.
but yes, in stock form the 13b will make more power. |
Also the 12a has left recipricating mass so can be made to rev to higher rpm with less stress.
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There are a lot of factors that contribute to an engine's power level, of coarse, but the biggies are compression and breathing. 13bs can move more air through each revolution and have a higher compression ratio. Also, he asked about stock porting. I don't think there can be much debate about which engine will make more power with bolt-ons.
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agreed, in stock port form the B motor will be stronger... but remember, the compression ratio is the same for the 12a and -se 13b.
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Originally Posted by FB II
the compression ratio is the same for the 12a and -se 13b.
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and which one will rev safely without trying to make itself a claymore, this is the reason for my having a 12a, because i have killed too many 13b's.
power trophy goes to the 13b by default. the 12a will take more work($$$) than a 13b for the same power, but the 13b won't last as long and service will be more often rambling a load of shit cos cant stop looking at the chick above- is that ur missus purple82? |
Originally Posted by sa22crotor
rambling a load of shit cos cant stop looking at the chick above- is that ur missus purple82?
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Originally Posted by purple82
It doesn't depend on if it's a 6 or 4 port.
yes it does. |
Originally Posted by wackyracer
yes it does.
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Originally Posted by gsterror
But you can't properly port the (is it exhaust or intake) ports on a 6 port.
With standalone, that port had 210rwhp potential with good tuning. His stage 2 streetport is also good for 220-230rwhp depending on tuning and exhaust. The guy that got 195rwhp before redline, with the stage 1 port, could have easily had more with a better exhaust setup and more fuel. Kahren himself got 185rwhp on a stock port 6 port. The 6 port is very open for some good numbers. |
This whole argument about 'less rotating mass', 'higher rev rpm', 'easier to port', is just crap.
Mazda chose to put the 13b in the SE's and EVERY RX7 THEREAFTER because it makes more power. End of argument. Trying to justify cost of modifications, porting, and all that is wasted time in the argument. The 12a was only implemented by Mazda in an attempt to get better fuel mileage in their fledgling sports car when they knew that would be a limitation for most new buyers in the market for a new car. With their efforts to make the 1981 and later motors with 'lean burn' carbs and cats to further help the emissions and fuel efficiency, this served to limit horsepower output considerably. Base numbers for stock motors: 12a = 105 HP/100ft/lbs torque - it's entire life span in the 1st Gen RX7 13b = 135 HP/133ft/lbs torque - ending at 255 HP through development in the 3rd Gen RX7 - STOCK. |
Originally Posted by LongDuck
The 12a was only implemented by Mazda in an attempt to get better fuel mileage in their fledgling sports car when they knew that would be a limitation for most new buyers in the market for a new car.
Base numbers for stock motors: 12a = 105 HP/100ft/lbs torque - it's entire life span in the 1st Gen RX7 12at = 165 HP/166ft/lbs torque Its just odd that if Mazda saw no future in the 12a that they would turbo it and add efi. Maybe a last horray or maybe they weren't so quick to kill it off in favor of the 13b. The other odd thing being that it was launched in Sept. of 1983, making it a 84' MY. Why canabalize the 13b sales? |
I thought the 12at was carb still, not EFI?
You can say the same thing about FC's, though. All jspec FC's were turbo, none were n/a. So why did Mazda have US spec ones as n/a and turbo? Because the US is a whole different market where emissions are stricter and fuel consumption are is more important to some people. |
Originally Posted by purple82
nope
cehck the weight difference between carb and F/I. |
Originally Posted by dDuB
I thought the 12at was carb still, not EFI?
You can say the same thing about FC's, though. All jspec FC's were turbo, none were n/a. So why did Mazda have US spec ones as n/a and turbo? Because the US is a whole different market where emissions are stricter and fuel consumption are is more important to some people. And the point I was trying to make was, why would Mazda dump money into an engine they had plans to axe two years from then. Not about the differences in the Japanese market vs. American. To simple add a turbo is one thing, but to make it EFI is another. Maybe they realized it wasn't the way to go, interesting none the less. |
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Looks carb to me? But maybe I'm wrong.
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the 12aT is NOT carb'd. it's a simple two injector tbi style injection.
longduck.. come on now, you can't keep comparing the later model B motors to the 12a because they added a TURBO. and they kept getting more RandD. the 12a WILL make the same power under even porting. as i said before, in stock form the damn ports are just straight up pathetic. tiny as all hell. if you bring them to the even size of the equivalent B motor and have the proper induction (carb/efi) you will be right there with it. in stock form there is obviously no comparison, but when porting is involved then it's really a matter of preference as you can make your hp goals on the 12a, no doubt. i've seen plenty of 250- 300rwhp n/a ported 12a's... you barely ever see a 6port 13b break 200rwhp. ;) |
the main reason i asked this question was i had a 84 GS about 5-6 yrs ago and it seemed like it had more power then my 84 SE and all i had done to it was remove the cat and straight pipe it. and on my SE i got it with headers, high flow cat , some kida muffler, light weight fly wheel, performance clutch, and an K&N airfilter. and i was thinking about go back to a 12A . but idont know if its the weight difference that makes it feel different or not!
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The power difference you are experiencing could be from a multitude of things, such as blocked cat, bad plugs or wires, vacuum leaks, fuel filter, carbon build up, loss of compression and so on. In bone stock condition your Se should have 30 more HP, from there on its just a matter of modification....
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i dont have a cmpression tester but when i pull the plugs it almost hurts my ears. iahve run sea foam through the fuel system a coule times so i dont think that its really carbon build up. i havent changed my fuel filter yet but i will very soon. and i dont kknow about my cat yet i might just gut it. i guess all get a can of carb cleaner and chk for leaks. plugs are still good. wires are less than a month old. i understand that the SE has 30 more hp but isnt there about a 200 lb difference too!
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The 0-60 reported by the car mags for the 79 was pretty close to the 84 SE. There's definitely benefits to light weight.
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